JP2011148073A - Mems sensor and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MEMS sensor with reduced variation, particularly in the electrical connectivity to an internal wiring layer and in the height of internal space, and the method for manufacturing thereof. <P>SOLUTION: The MEMS sensor includes: a first substrate 21; a second substrate 22; a first SiO<SB>2</SB>layer 25 formed on the surface of the first substrate 21; the internal wiring layer 24 formed between the first substrate 21 and the first SiO<SB>2</SB>layer 25; a through-hole 26 formed through a portion from a surface 25a of the first SiO<SB>2</SB>layer 25 to the internal wiring layer 24; an electric connection layer 28 formed in the through-hole 26 so as to be electrically connected to the internal wiring layer 24; and a first silicon nitride layer 33 with a protruding shape, located between the second substrate 22 and the first SiO<SB>2</SB>layer 25 so as to regulate the height of the internal space S2 formed between the second substrate 22 and the first substrate 21. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a MEMS sensor in which a first substrate and a second substrate are arranged at an interval in the height direction.

  Patent Document 1 discloses a MEMS sensor in which two opposing substrates are bonded via a metal bonding portion. The joining portion is a sealing layer, thereby forming an internal space between the two substrates.

  However, in the invention described in Patent Document 1, it is considered that it is difficult to adjust the height dimension between two substrates with high accuracy because the joint is solder. In Patent Document 1, it is not assumed that one of the two substrates is configured as a wiring substrate.

Fig.6 (a) has shown the fragmentary longitudinal cross-section of the MEMS sensor of the comparative example with respect to this invention.
As shown in FIG. 6A, the SiO ₂ layer 2 is formed on the surface of the first substrate 1, and the internal wiring layer 3 is formed on the surface of the SiO ₂ layer 2. A silicon nitride layer 4 is formed from the SiO ₂ layer 2 to the internal wiring layer 3. As shown in FIG. 6A, the silicon nitride layer 4 has a through hole 4a leading to the internal wiring layer 3, and an electrical connection layer 5 is formed in the through hole 4a. A through hole 6 is formed from the silicon nitride layer 4 to the SiO ₂ layer 2, and an electrical connection layer 7 is formed in the through hole 6 communicating with the first substrate 1.

  As shown in FIG. 6A, a protrusion 4b is formed in the silicon nitride layer 4, and the protrusion 4b is formed with a height dimension L1 (cavity height).

  As shown in FIG. 6A, the second substrate 8 and the protruding portion 4 b are bonded via a bonding portion 9.

  In the MEMS sensor of the comparative example shown in FIG. 6A, the first substrate 1 side can be configured as a wiring substrate. Further, the interval of the internal space S1 can be regulated by the height dimension L1 of the protrusion 4b of the silicon nitride layer 4.

However, the structure of the MEMS sensor shown in FIG. 6A has the following problems. That is, the silicon nitride layer 4 has a higher etching rate than the SiO ₂ layer 2 and the internal wiring layer 3 (for example, AlCu), and in the process of forming the through holes 4a and 6 shown in FIG. Is also over-etched in the lateral direction, and a reverse tapered surface as shown in FIG. 6B (partially enlarged longitudinal sectional view showing a portion surrounded by a dotted line A in FIG. 6A) on the side surface of the silicon nitride layer 4 There was a problem that 10 was formed. As a result, when the electrical connection layers 5 and 7 are embedded in the through holes 4 a and 6, the adhesion on the reverse tapered surface 10 is poor, so that disconnection is likely to occur near the reverse tapered surface 10. In addition, a gap is formed in the vicinity of the reverse taper surface 10, and stress is easily generated in the vicinity of the reverse taper surface 10 when a heat treatment process or the like is performed, which easily causes disconnection or peeling.

  In the MEMS sensor shown in FIG. 6A, the protrusion 4b is formed by etching the silicon nitride layer 4 halfway. With this configuration, the height L1 of the protrusion 4b is likely to vary. It was found that a variation of about 0.5% to 8% (variation with respect to the reference height dimension L1) occurs. As described above, when the height L1 of the protrusion 4b varies, the interval of the internal space S1 varies. For example, in the configuration in which the movable portion displaceable in the height direction is formed on the second substrate 8, the gap length L2 of the movable portion in the internal space S1 varies due to the variation in the height dimension L1 of the protrusion 4b. This leads to deterioration or variation in detection characteristics, which is not preferable.

On the other hand, when the portion of the silicon nitride layer 4 is also a SiO ₂ layer, the etching rate of the SiO ₂ layer for very slow, very time consuming for the formation of the projecting portion 4b, also the height dimension L1 not only in the plane Dimensional variation in the direction is also likely to occur. Further, since the stress of the SiO ₂ layer is large, the second substrate 8 and the protruding portion 4b are easily peeled off.

JP 2005-236159 A

  The present invention solves the above-described conventional problems, and in particular, a MEMS sensor capable of improving the stability of electrical wiring and further reducing variations in the height dimension of the internal space, and its The object is to provide a manufacturing method.

The MEMS sensor in the present invention is
Formed between the first substrate, the second substrate, the first SiO ₂ layer formed on the surface of the first substrate, and the first substrate and the first SiO ₂ layer. An internal wiring layer, a through hole formed from the surface of the first SiO ₂ layer to the internal wiring layer, an electrical connection layer formed in the through hole and electrically connected to the internal wiring layer, , A projecting-shaped second member positioned between the second substrate and the first SiO ₂ layer and restricting a height dimension of an internal space formed between the second substrate and the first substrate. 1 silicon nitride layer.

In the present invention, a through-hole for forming an electrical connection layer that leads to the internal wiring layer is formed in the first SiO ₂ layer without being formed in the first silicon nitride layer, so that the protruding first silicon nitride layer is formed. Was formed on the first SiO ₂ layer as a regulating layer for regulating the height dimension of the internal space. Thereby, it can suppress that a reverse taper surface is formed in the side surface of a through-hole like a comparative example, and can suppress the disconnection of an electrical-connection layer. Moreover, the variation in the height dimension of the internal space can be reduced. Furthermore, the stress can be relieved by bonding the protruding first silicon nitride layer having a lower stress than the SiO ₂ layer and the second substrate, and defects such as peeling between the substrates can be suppressed.

  In the present invention, the first silicon nitride layer can function as a sealing layer surrounding the periphery of the second substrate.

  In the present invention, the internal wiring layer is led out from the inside of the first silicon nitride layer where the electrical connection layer is formed to the outside of the first silicon nitride layer. It is preferable to be electrically connected to the external connection layer outside the silicon layer.

In the present invention, the second substrate includes an anchor portion, a movable portion supported by the anchor portion so as to be displaceable in a height direction, and a frame body portion formed around the anchor portion and the movable portion. A support substrate fixed to the anchor portion and the frame portion is provided on the opposite side of the second substrate facing the first substrate,
The frame portion and the first silicon nitride layer on the first SiO ₂ layers are formed, the second silicon nitride layer of the protruding shape is formed on the said anchor portion first SiO ₂ layers The first silicon nitride layer and the frame body layer, and the second silicon nitride layer and the anchor portion are preferably applied by eutectic bonding with a metal layer.

  In the present invention, the second silicon nitride layer bonded to the anchor portion can be formed with the same height as the first silicon nitride layer. Also, the first silicon nitride layer and the frame body layer and the second silicon nitride layer and the anchor portion can be firmly bonded by eutectic bonding.

In the above configuration, a fixed electrode layer extending from the electrical connection layer to a position facing the movable portion can be formed on the surface of the first SiO ₂ layer. As a result, a MEMS sensor using a capacitance change between the movable part and the fixed electrode layer can be configured.

Alternatively, in the above configuration, a fixed electrode layer facing the movable portion is formed on the same formation surface as the internal wiring layer, and the fixed electrode layer is formed to be exposed from the first SiO ₂ layer. However, the reliability of the MEMS sensor can be improved, which is more preferable.

  Further, in the present invention, a joint portion made of the metal layer formed between the anchor portion and the second silicon nitride layer is connected to the internal wiring layer as the electrical connection layer in the through hole. Can be preferably applied.

  In the present invention, it is preferable that the second substrate and the first silicon nitride layer are eutectic bonded by a metal layer. Thereby, the space between the first substrate and the second substrate can be appropriately sealed.

Or the MEMS sensor in this invention is
A first substrate, a second substrate, and a support substrate formed on the opposite side of the second substrate facing the first substrate,
The second substrate includes an anchor portion, a movable portion supported by the anchor portion so as to be displaceable in a height direction, and a frame body portion formed around the anchor portion and the movable portion. Configured, the anchor portion and the frame body portion and the support substrate are fixed,
An insulating layer is formed on the surface of the first substrate facing the second substrate, and the insulating layer protrudes at a position facing the anchor portion and the frame portion, and the insulating layer and the anchor The eutectic bonding between the parts, and between the insulating layer and the frame part by a metal layer,
An internal wiring layer is formed in the insulating layer, a fixed electrode layer facing the movable portion is formed on the same surface as the internal wiring layer, and the fixed electrode layer is exposed from the insulating layer. It is characterized by being formed.

  As a result, the stability of the electrical wiring can be improved, and a highly reliable MEMS sensor can be obtained.

  Further, in the above configuration, a through hole is formed in the insulating layer at a position facing the internal wiring layer, and the metal formed between the internal wiring layer, the insulating layer, and the anchor portion through the through hole. It is preferable that the junction part which consists of a layer is connected.

In the present invention, the second SiO ₂ layer is formed on the surface of the first substrate, the said internal wiring layer is formed on the surface of the second SiO ₂ layer, the second from the internal wiring layer it to the structure over the SiO ₂ layer on the first SiO ₂ layer is formed. As a result, the first substrate and the internal wiring layer can be appropriately electrically insulated. Also by providing the second SiO ₂ layer of the same etching rate under the first SiO ₂ layer, the reverse tapered surface when forming a through hole from the first SiO ₂ layer over the second SiO ₂ layer The through-holes can be appropriately formed without the formation of etc.

Moreover, the manufacturing method of the MEMS sensor in the present invention is as follows.
Forming an internal wiring layer on one surface side of the first substrate and forming a first SiO ₂ layer from the surface of the first substrate over the internal wiring layer;
Forming a silicon nitride layer overlying the first SiO ₂ layer;
Removing the unnecessary silicon nitride layer to form a protruding first silicon nitride layer;
Forming a through hole communicating with the internal wiring layer in the first SiO ₂ layer, and forming an electrical connection layer electrically connected to the internal wiring layer in the through hole;
A second substrate is disposed opposite to the first substrate, and at this time, a height dimension of an internal space formed between the first substrate and the second substrate is set to the first silicon nitride layer. The process of regulating by the height dimension of
It is characterized by having.

  According to the MEMS sensor manufacturing method of the present invention, it is possible to suppress the formation of a reverse tapered surface on the side surface of the through hole as in the comparative example, and it is possible to suppress disconnection of the electrical connection layer. In addition, the height dimension of the first silicon nitride layer can be regulated with high accuracy, and variations in the height dimension of the internal space can be reduced.

  According to the MEMS sensor and the manufacturing method thereof of the present invention, it is possible to suppress the formation of a reverse tapered surface on the side surface of the through hole, and it is possible to suppress disconnection of the electrical connection layer. In addition, the height dimension of the first silicon nitride layer can be regulated with high accuracy, and variations in the height dimension of the internal space can be reduced. In the present invention, the stability of electrical wiring can be improved, and a MEMS sensor having excellent reliability can be obtained.

The schematic diagram (longitudinal sectional view) of the MEMS sensor of the first embodiment of the present invention, FIG. 1 is a process diagram (longitudinal sectional view) showing a manufacturing method of the wiring board of the MEMS sensor shown in FIG. Schematic diagram (longitudinal sectional view) of the MEMS sensor of the second embodiment of the present invention, Schematic diagram (longitudinal sectional view) of a MEMS sensor according to a third embodiment of the present invention, A schematic diagram (longitudinal sectional view) of a MEMS sensor according to a fourth embodiment of the present invention, Schematic diagram (longitudinal sectional view) of the MEMS sensor in the comparative example,

  FIG. 1 is a schematic diagram (longitudinal sectional view) of the MEMS sensor according to the first embodiment of the present invention, FIG. 2 is a process diagram (longitudinal sectional view) showing a manufacturing method of the wiring board of the MEMS sensor shown in FIG. FIG. 4 is a schematic view (longitudinal sectional view) of a MEMS sensor according to a second embodiment of the present invention, FIG. 4 is a schematic view (longitudinal sectional view) of a MEMS sensor according to a third embodiment of the present invention, and FIG. It is a schematic diagram (longitudinal sectional view) of the MEMS sensor according to the fourth embodiment.

  As shown in FIG. 1, the MEMS sensor 20 includes a first substrate 21 and a second substrate 22. Both the first substrate 21 and the second substrate 22 are made of silicon.

As shown in FIG. 1, a second SiO ₂ layer 23 is formed on the entire surface 21 a of the first substrate 21. An internal wiring layer 24 is formed on the surface 23 a of the second SiO ₂ layer 23. The material of the internal wiring layer 24 is not particularly limited, but is formed of, for example, AlCu. As shown in FIG. 1, the internal wiring layer 24 is formed extending in the X direction.

As shown in FIG. 1, a first SiO ₂ layer 25 is formed from the second SiO ₂ layer 23 to the internal wiring layer 24. As a result, the internal wiring layer 24 is buried in the SiO ₂ layer. The surface 25a of the first SiO ₂ layer 25 is a planarized surface.

As shown in FIG. 1, through holes 26 and 27 are formed in the first SiO ₂ layer 25 at positions facing the internal wiring layer 24. The through hole 26 is formed on the inner side (inside the internal space S <b> 2) surrounded by a first silicon nitride layer 33 described later, and the through hole 27 is formed on the outer side of the first silicon nitride layer 33.

As shown in FIG. 1, the inside of the through hole 26 is filled with an electrical connection layer 28 made of a conductive material. In addition, a fixed electrode layer 29 is integrally formed from the electrical connection layer 28 and extends to the surface 25 a of the first SiO ₂ layer 25. The interior of the through hole 27 is also filled with the electrical connection layer 46. An output signal external connection layer 30 is formed integrally with the electrical connection layer 46 and extending to the surface 25 a of the first SiO ₂ layer 25.

As shown in FIG. 1, a continuous through hole 31 is formed from the first SiO ₂ layer 25 to the second SiO ₂ layer 23. The through hole 31 communicates with the surface 21 a of the first substrate 21. The inside of the through hole 31 is filled with an electrical connection layer 32. The surface of the electrical connection layer 32 is exposed on the surface 25 a of the first SiO ₂ layer 25.

  Each of the through holes 26, 27, and 31 has a tapered surface so that the interval gradually decreases from the upper surface side toward the lower surface direction (the first substrate 21 direction).

  The material of each electrical connection layer 28, 32, 46, fixed electrode layer 29, and external connection layer 30 is not particularly limited, but a material excellent in conductivity is preferably applied.

As shown in FIG. 1, a protruding first silicon nitride layer 33 is formed on the surface 25 a (flattened surface) of the first SiO ₂ layer 25. The first silicon nitride layer 33 is formed in a frame shape in plan view. In the embodiment shown in FIG. 1, the fixed electrode layer 29 and the electrical connection layer 32 are exposed in a space (cavity) surrounded by the first silicon nitride layer 33, and the protruding second silicon nitride layer 34 is further formed. Is provided. Both the first silicon nitride layer 33 and the second silicon nitride layer 34 are formed with a height of L3. Here, the height dimension L3 is defined by the height dimension from the surface 25a of the first SiO ₂ layer 25 to the upper surface of the first silicon nitride layer 33. The first silicon nitride layer 33 and the second silicon nitride layer 34 are SiN, SiNx, or the like.

  The longitudinal cross-sectional shapes of the first silicon nitride layer 33 and the second silicon nitride layer 34 are both substantially trapezoidal. That is, the width dimension between the both side surfaces of the silicon nitride layer gradually decreases from the lower surface toward the upper surface.

  A wiring substrate 45 is configured by a laminated structure from the first substrate 21 shown in FIG. 1 to a first metal layer 43 formed on the surfaces of silicon nitride layers 33 and 34 described later.

  As shown in FIG. 1, the second substrate 22 is fixedly supported on a support substrate 36 via an oxide insulating layer (ceramic layer) 35 on the opposite surface side of the first substrate 21. An SOI (Silicon on Insulator) substrate can be formed by the second substrate 22, the oxide insulating layer 35, and the support substrate 36. The support substrate 36 is made of silicon.

  As shown in FIG. 1, the second substrate 22 includes an anchor portion 37, a movable portion 38, a spring portion 39, and a frame body portion 40. Each part can be configured by etching the second substrate 22. The movable part 38 is supported by the anchor part 37 via a spring part 39 so as to be displaceable in the height direction (Z). The movable part 38 and the frame part 40 are separated. The planar shape of the frame body portion 40 is substantially the same as that of the first silicon nitride layer 33, and the frame body portion 40 and the first silicon nitride layer 33 face each other in the height direction (Z).

As shown in FIG. 1, the oxide insulating layer 35 is not formed between the movable portion 38 and the spring portion 39 and the support substrate 36. Therefore, the movable portion 38 can be displaced in the height direction (Z). The oxide insulating layer 35 is preferably formed of SiO ₂ .

  As shown in FIG. 1, one movable portion 38 is in a position facing the fixed electrode layer 29 in the height direction (Z). The other movable portion 38 is at a position facing the electrical connection layer 32 at the ground potential. For this reason, when the movable part 38 is displaced in the height direction (Z), the distance between the fixed electrode layer 29 and the electrical connection layer 32 is changed to change the electrostatic capacity, and the electrostatic capacity change is caused by the external connection layer 30. For example, it is possible to detect a change in acceleration and the magnitude of acceleration by detecting with an electric circuit.

  As shown in FIG. 1, joint portions 41 and 42 formed of a metal layer are formed between the first silicon nitride layer 33 and the frame portion 40 and between the second silicon nitride layer 34 and the anchor portion 37. Has been. As shown in FIG. 1, the joint portions 41 and 42 are obtained by eutectic bonding of a first metal layer 43 and a second metal layer 44. One of the first metal layer 43 and the second metal layer 44 is preferably formed of Al (aluminum) and the other is formed of Ge (germanium).

As shown in FIG. 1, the first metal layer 43 of the junction 42 interposed between the anchor portion 37 and the second silicon nitride layer 34 is formed over the side surface of the second silicon nitride layer 34 and is not shown. It extends to the wiring layer. The wiring layer is connected to an internal wiring layer (not shown) buried in the SiO ₂ layers 23 and 25 and is electrically drawn out to the outside.

FIG. 2 is a process diagram showing a method of manufacturing the wiring board 45 shown in FIG. In the step shown in FIG. 2A, a second SiO ₂ layer 23 is formed on a first substrate 21 made of silicon, and an internal wiring layer 24 is formed in a predetermined region on the second SiO ₂ layer 23. Form. Then, a first SiO ₂ layer 25 is formed from the internal wiring layer 24 to the second SiO ₂ layer 23.

Next, in the step of FIG. 2B, the surface 25a of the first SiO ₂ layer 25 is flattened by a CMP technique or the like. 2A and 2B, the internal wiring layer 24 is embedded in the SiO ₂ layer.

Next, in the step of FIG. 2C, a silicon nitride layer 50 is formed on the surface 25 a of the first SiO ₂ layer 25.

2D, unnecessary silicon nitride layer 50 is removed by etching, and first silicon nitride layer 33 and second silicon nitride having a protruding shape on surface 25a of first SiO ₂ layer 25 are removed. Leave layer 34. The first silicon nitride layer 33 is formed in a frame shape in plan view, and a space (cavity) surrounded by the first silicon nitride layer 33 can be formed. The second silicon nitride layer 34 is formed in a region facing the anchor portion 37 formed on the second substrate 22 (see FIG. 1).

Next, in the step shown in FIG. 2E, through holes 26 and 27 communicating with the internal wiring layer 24 are formed in the first SiO ₂ layer 25 by etching. The through hole 26 is formed inside the space surrounded by the first silicon nitride layer 33, and the through hole 27 is formed outside. Simultaneously with the formation of the through holes 26 and 27, the through hole 51 is formed in the first SiO ₂ layer 25.

  Next, in the step of FIG. 2F, the through hole 51 is further deeply etched to form a through hole 31 that leads to the first substrate 21. Since the through hole 31 is formed by etching twice, a step is formed on the side surface of the through hole 31.

Next, in the step of FIG. 2G, the conductive layer 52 is formed on the first silicon nitride layer 33, the second silicon nitride layer 34, and the entire region of the first SiO ₂ layer 25 by sputtering or the like. Form. At this time, the through holes 26, 27, 31 are also filled with the conductive layer 52.

Next, in the step of FIG. 2H, the unnecessary conductive layer 52 is removed by etching. As a result, the electrical connection layer 28 electrically connected to the internal wiring layer 24 in the through hole 26 and the fixed electrode layer 29 formed integrally with the electrical connection layer 28 can be formed. Furthermore, the electrical connection layer 46 electrically connected to the internal wiring layer 24 in the through hole 27 and the external connection layer 30 formed integrally with the electrical connection layer 46 can be formed. Furthermore, an electrical connection layer 32 connected to the first substrate 21 can be formed in the through hole 31. A first metal layer 43 can be formed on the first silicon nitride layer 33 and the second silicon nitride layer 34. The first metal layer 43 formed on the second silicon nitride layer 34 is formed integrally with a wiring layer (not shown) formed on the first SiO ₂ layer 25.

  In this way, the wiring board 45 can be formed. Subsequently, the second substrate 22 including the anchor portion 37, the movable portion 38, and the frame body portion 40 and the wiring substrate 45 are eutectic bonded by the first metal layer 43 and the second metal layer 44. At this time, a predetermined heat treatment is performed so as to cause eutectic bonding appropriately between the first metal layer 43 and the second metal layer 44.

According to the MEMS sensor 20 of the present embodiment, the through holes 26 and 27 leading to the internal wiring layer 24 are formed in the first SiO ₂ layer 25 and are not formed in the silicon nitride layer. A protruding first silicon nitride layer 33 is formed on the first SiO ₂ layer 25 as a restricting layer that restricts the height dimension of the internal space S2.

The through holes 26 and 27 are very narrow spaces surrounded except for the upper surface, so that an etching gas (for example, CF ₄ gas) at the time of etching tends to accumulate in the through holes, and the silicon nitride having a high etching rate (fast) When a through-hole having a narrow space is formed in the layer, etching proceeds in the lateral direction due to retention of the etching gas, and the reverse tapered surface 10 is easily formed like the side surface of the silicon nitride layer 4 shown in FIG. In contrast, in the present embodiment, the through holes 26 and 27, is low (slow) etch rates of the SiO ₂ layer than silicon nitride layer through holes 26, 27 formed on the first SiO ₂ layer 25 Therefore, it is possible to suppress the formation of reverse tapered surfaces in the through holes 26 and 27, the through holes 26 and 27 can be appropriately filled with a conductive material, and the disconnection of the electrical connection layers 28 and 46 can be suppressed. I can do it. In addition, the formation of voids in the electrical connection layers 28 and 46 can be suppressed, and it is possible to appropriately prevent problems such as disconnection of the electrical connection layers 28 and 46 due to heat treatment for eutectic bonding. I can do it.

In the embodiment shown in FIG. 1, the first SiO ₂ layer 25 and the second SiO ₂ layer 23 have a two-layer structure, and the first SiO ₂ layer 25 and the second SiO ₂ layer 23 are continuous. Although the hole 31 is formed, it is possible to suppress the reverse tapered surface from being formed in the through hole 31, and the disconnection of the electrical connection layer 32 can be suppressed.

  Therefore, in this embodiment, the stability of the electrical wiring can be improved as compared with the comparative example, and a MEMS sensor having excellent reliability can be obtained.

Further, in the structure of the MEMS sensor 20 of the embodiment shown in FIG. 1, the variation in the height dimension of the internal space S2 can be reduced. In the step of FIG. 2D, the unnecessary silicon nitride layer 50 is removed by etching. At this time, since the first SiO ₂ layer 25 having a low (slow) etching rate serves as a stopper (the first SiO ₂ layer 25 may be over-etched to some extent), in this embodiment, The height dimension L3 from the surface 25a of the SiO ₂ layer 25 to the upper surface of the protruding first silicon nitride layer 33 is substantially regulated by the film thickness at the time of film formation of the silicon nitride layer 50 shown in FIG. I can do it. In the present embodiment, it was found that the variation in the height dimension L3 can be reduced to around 1%.

  As shown in FIG. 1, the height dimension of the internal space S2 is a dimension obtained by adding the height dimension L3 of the first silicon nitride layer 33 and the film thickness of the bonding portion 41. The thickness is much smaller than the height dimension L3, and therefore the height dimension of the internal space S2 can be determined approximately by the height dimension L3 of the first silicon nitride layer 33.

In this embodiment, the stress can be relieved by bonding the silicon nitride layers 33 and 34 and the second substrate 22, which have a lower stress than the SiO ₂ layer, and defects such as peeling between the substrates can be suppressed.

  In the embodiment shown in FIG. 1, the first silicon nitride layer 33 and the second silicon nitride layer 34 bonded to the anchor portion 37 on the wiring substrate 45 side have the same film thickness as the first silicon nitride layer 33. Can be formed. In the present embodiment, the first silicon nitride layer 33 and the frame body portion 40 and the second silicon nitride layer 34 and the anchor portion 37 are firmly bonded by eutectic bonding of the bonding portions 41 and 42. I can do it.

  Although the fixed electrode can be formed on the second substrate 22 side together with the movable portion 38 (for example, the movable portion 38 is a comb-like electrode, and a comb-like fixed electrode is interposed between the electrodes), In the embodiment, the fixed electrode layer 29 can be easily and appropriately formed on the wiring board 45 side as shown in FIG. 1, and the MEMS sensor 20 using the capacitance change between the movable portion 38 and the fixed electrode layer 29 is appropriately configured. I can do it.

Further, the second SiO ₂ layer 23 may not be formed under the first SiO ₂ layer 25, but the internal wiring layer 24 can be appropriately embedded in the SiO ₂ layer by the configuration of FIG. . Also under the first SiO ₂ layer 25, by forming the second SiO ₂ layer 23 of the same etching rate, the through-hole 31 which is formed from a first SiO ₂ layer 25 over the second SiO ₂ layer 23 Therefore, it is possible to suppress the problem that the reverse tapered surface is formed.

  FIG. 3 is a schematic diagram (longitudinal sectional view) of the MEMS sensor according to the second embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In FIG. 3, the illustration of the spring portion 39 and the electrical connection layer 32 at the ground potential shown in FIG. 1 is omitted.

Also in this embodiment, the internal wiring layer 24 is embedded in the SiO ₂ layers 23 and 25 formed on the first substrate 21 side as in FIG.

In the embodiment shown in FIG. 3, the fixed electrode layer 29 is formed on the surface 23 a of the second SiO ₂ layer 23, which is the same formation surface as the internal wiring layer 24. The fixed electrode layer 29 is formed so as to be exposed from the first SiO ₂ layer 25 covering the internal wiring layer 24.

Further, protruding silicon nitride layers 33 and 34 are formed on the first SiO ₂ layer 25.

By the way, in this embodiment, since the through hole is formed in the first SiO ₂ layer 25 having a lower (slower) etching rate than the silicon nitride layer, the formation of a reverse tapered surface in the through hole is suppressed. However, the conductive material may be thinly attached in the through hole, especially the deterioration of the contact due to the shape change of the minute through hole, the thermal stress at the time of eutectic bonding, and the etching agent used at the time of pattern formation adheres. In some cases, the reliability of the MEMS sensor may be reduced, such as disconnection or increase in wiring resistance.

Therefore, in the embodiment shown in FIG. 3, the first SiO ₂ layer formed in the portion facing the movable portion 38 is removed to expose a part of the wiring layer, and the exposed part of the wiring layer is fixed to the fixed electrode layer. 29. Therefore, in FIG. 3, it is not necessary to connect the fixed electrode layer 29 and the internal wiring layer in the height direction via the through hole. Therefore, the stability of the electrical wiring can be improved more effectively, and the MEMS sensor 20 having excellent reliability can be obtained.

On the other hand, as shown in FIG. 3, the internal wiring layer 24 is bonded to the anchor portion 37 and the second silicon nitride layer 34 through the through holes 60, 60 formed in the first SiO ₂ layer 25. The unit 42 is connected. In this portion, a part of the metal layer constituting the joint 42 is likely to flow into the through hole 60 by heat treatment during eutectic bonding. Therefore, the through hole 60 can be appropriately filled with a conductive material, and stable electrical connectivity can be obtained between the joint portion 42 and the internal wiring layer 24.

  FIG. 4 is a schematic diagram (longitudinal sectional view) of the MEMS sensor according to the third embodiment of the present invention. 1 and 3 are denoted by the same reference numerals as in FIG. In FIG. 4, the illustration of the spring part 39 and the electrical connection layer 32 at the ground potential shown in FIG. 1 is omitted.

In the embodiment shown in FIG. 4, the SiO ₂ layer 61 is formed on the first substrate 21, and the internal wiring layer 24 is formed on the SiO ₂ layer 61. A fixed electrode layer 29 is formed on the surface 61 a of the SiO ₂ layer 61, which is the same formation surface as the internal wiring layer 24.

In the embodiment shown in FIG. 4, the internal wiring layer 24 is filled with an insulating layer 62. The insulating layer 62 is a SiO ₂ layer, a silicon nitride layer, or the like. On the surface of the insulating layer 62, a portion facing the anchor portion 37 and the frame body portion 40 protrudes, and the other portion is a concave cavity portion.

  In the embodiment shown in FIG. 4, as in FIG. 3, the insulating layer 62 formed in the portion facing the movable portion 38 is removed to expose a part of the wiring layer, and the exposed wiring layer portion is fixed to the fixed electrode. Layer 29 is provided. Therefore, in FIG. 4, it is not necessary to connect the fixed electrode layer 29 and the internal wiring layer in the height direction via the through hole. Therefore, the stability of the electrical wiring can be improved more effectively, and the MEMS sensor 20 having excellent reliability can be obtained.

  Also in the embodiment shown in FIG. 4, as in FIG. 3, the internal wiring layer 24 and the joint portion 42 that joins between the anchor portion 37 and the insulating layer 62 through the through holes 63, 63 formed in the insulating layer 62. Is connected. In this portion, a part of the joint portion 42 is likely to flow into the through hole 63 by heat treatment during eutectic bonding. For this reason, the through-hole 63 can be appropriately filled with a conductive material, and stable electrical connectivity can be obtained between the joint portion 42 and the internal wiring layer 24.

In the embodiment shown in FIG. 3, the surface of the first SiO ₂ layer 25 is opposed to the movable portion 38. In the embodiment shown in FIG. 4, the surface of the insulating layer 62 is opposed to the movable portion 38. Protrusions 65 are formed at the respective locations. The protrusion 65 has a function of suppressing the movable part 38 from being displaced by a predetermined amount or more in the height direction and a function of preventing sticking.

In the embodiment shown in FIGS. 3 and 4, the first SiO ₂ layer 25 and the insulating layer 62 covering the fixed electrode layer 29 in the manufacturing process are not completely removed, and a part is left as the protrusion 65. The protrusion 65 can also be provided on the fixed electrode layer 29.

FIG. 5 shows a partial longitudinal sectional view of a MEMS sensor showing an embodiment different from FIG. In FIG. 5, the internal wiring layer 24 is formed on the first substrate 21 via an electrically insulating base layer 53. The underlayer 53 may be other than the SiO ₂ layer. As shown in FIG. 3, a first SiO ₂ layer 25 is formed on the internal wiring layer 24. The first SiO ₂ layer 25 is formed with through holes 26 and 27 communicating with the internal wiring layer 24. Electrical connection layers 28 and 46 are formed in the through holes 26 and 27.

In the embodiment shown in FIG. 5, a frame-shaped first silicon nitride layer 33 is formed on the first SiO ₂ layer 25 so as to protrude in a plan view. Then, a second substrate 55 is formed on the first silicon nitride layer 33 via a joint 41 by eutectic bonding. As a result, an internal space S3 is formed between the first substrate 21 and the second substrate 55, and the height dimension of the internal space S3 is appropriately regulated by the height dimension (film thickness) of the first silicon nitride layer 33. I can do it.

  In the embodiment shown in FIG. 5, the sensor element 56 is installed in the internal space S3, and the connection terminal portion 57 of the sensor element 56 is electrically connected to the electrical connection layer 46 (in FIG. 3). The connection state of one of the connection terminals is shown).

20 MEMS sensor 21 First substrate 22, 55 Second substrate 23 Second SiO ₂ layer 24 Internal wiring layer 25 First SiO ₂ layer 26, 27, 31, 51, 60, 63 Through holes 28, 32, 46 Electrical connection layer 29 Fixed electrode layer 30 External connection layer 33 First silicon nitride layer 34 Second silicon nitride layer 35 Oxide insulating layer 36 Support substrate 37 Anchor part 38 Movable part 40 Frame part 41, 42 Junction part 45 Wiring Substrate 50 Silicon nitride layer 52 Conductive layer 53 Underlayer 56 Sensor element 61 SiO ₂ layer 62 Insulating layer 65 Projection

Claims (10)

Formed between the first substrate, the second substrate, the first SiO ₂ layer formed on the surface of the first substrate, and the first substrate and the first SiO ₂ layer. An internal wiring layer, a through hole formed from the surface of the first SiO ₂ layer to the internal wiring layer, an electrical connection layer formed in the through hole and electrically connected to the internal wiring layer, , A projecting-shaped second member positioned between the second substrate and the first SiO ₂ layer and restricting a height dimension of an internal space formed between the second substrate and the first substrate. And a silicon nitride layer.   The MEMS sensor according to claim 1, wherein the first silicon nitride layer functions as a sealing layer that surrounds the periphery of the second substrate.   The internal wiring layer is drawn out from the inside of the first silicon nitride layer where the electrical connection layer is formed to the outside of the first silicon nitride layer, and the outside of the first silicon nitride layer The MEMS sensor according to claim 1, wherein the MEMS sensor is electrically connected to the external connection layer. The second substrate includes an anchor portion, a movable portion supported by the anchor portion so as to be displaceable in a height direction, and a frame body portion formed around the anchor portion and the movable portion. And a support substrate fixed to the anchor portion and the frame body portion is provided on the opposite side of the second substrate facing the first substrate,
The frame portion and the first silicon nitride layer on the first SiO ₂ layers are formed, the second silicon nitride layer of the protruding shape is formed on the said anchor portion first SiO ₂ layers 4. The eutectic bonding of the first silicon nitride layer and the frame body layer and between the second silicon nitride layer and the anchor portion by a metal layer. The MEMS sensor according to 1. 5. The MEMS sensor according to claim 4, wherein a fixed electrode layer is formed extending from the electrical connection layer to a position facing the movable portion on the surface of the first SiO ₂ layer. The MEMS according to claim 4, wherein a fixed electrode layer facing the movable portion is formed on the same formation surface as the internal wiring layer, and the fixed electrode layer is formed so as to be exposed from the first SiO ₂ layer. Sensor.   7. The joint portion made of the metal layer formed between the anchor portion and the second silicon nitride layer is connected to the internal wiring layer as the electrical connection layer in the through hole. The MEMS sensor according to any one of the above.   4. The MEMS sensor according to claim 1, wherein the second substrate and the first silicon nitride layer are eutectic bonded by a metal layer. 5. The second SiO ₂ layer is formed on the surface of the first substrate, wherein the surface of the second SiO ₂ layer internal wiring layer is formed, the second SiO ₂ layer on the said internal wiring layer The MEMS sensor according to any one of claims 1 to 8, wherein the first SiO ₂ layer is formed over the top. Forming an internal wiring layer on one surface side of the first substrate and forming a first SiO ₂ layer from the surface of the first substrate over the internal wiring layer;
Forming a silicon nitride layer overlying the first SiO ₂ layer;
Removing the unnecessary silicon nitride layer to form a protruding first silicon nitride layer;
Forming a through hole communicating with the internal wiring layer in the first SiO ₂ layer, and forming an electrical connection layer electrically connected to the internal wiring layer in the through hole;
A second substrate is disposed opposite to the first substrate, and at this time, a height dimension of an internal space formed between the first substrate and the second substrate is set to the first silicon nitride layer. The process of regulating by the height dimension of
A method for manufacturing a MEMS sensor, comprising:

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